1. Field of Invention
This invention relates to scaffolding planks. More specifically, this invention is directed to a composite scaffolding plank and a method for forming the same. The composite scaffolding plank is an improved, low cost wide scaffolding plank formed by pinning and anchoring a plurality of narrow wooden boards, at least one of which is a whole natural wooden board and at least one of which is a laminated wooden board. In addition, the strength of a wooden plank may be improved by cutting the plank longitudinally into sections, adding at least one laminated wooden board and pinning the plank sections together as described above.
2. Related Art
Prior to this invention, two types of scaffolding planks existed in the prior art: the solid single board plank and the laminated plank. The solid single board plank comprises one wide wooden board. The laminated plank is constructed from multiple layers of wooden strips glued together. Each of the two types of prior art scaffolding planks have advantages and disadvantages.
With respect to the disadvantages, due to the limited resources of old growth forests and the harvesting schemes for new growth timber, the yield of wooden boards wide enough from which to construct a solid single board plank is decreasing. Typically, only the center portion of a large tree is sufficiently broad to produce a solid single board plank. Thus, with decreasing yield, the solid single board planks are becoming more costly and difficult to make. The main disadvantage of laminated planks is that laminated planks primarily consist of glued layers of wooden strips, which glued layers of wooden strips absorb substantial amounts of moisture. After absorbing enough moisture, the wooden fibers of the laminated plank soften and the moisture hastens decay in the scaffolding board. Likewise, any time one of the veneers of the laminated plank cracks, the laminated plank looses its strength and consistency and can also no longer be used as a scaffolding.
With respect to the advantages, the solid single board planks are comparatively stronger and easier to manufacture than the laminated planks. In turn, the laminated planks, if oriented correctly, are comparitively more rigid than the solid single board planks. Moreover, laminated planks, when used in dry conditions, do not shrink as much as solid single board planks.
Co-pending application entitled Composite Scaffolding Plank and Method for Forming Same, which was filed on even date herewith, provides a safe third alternative to the solid single board plank and the laminated plank and reduces, if not eliminates, the disadvantages of the two types of prior art planks. However, the plank disclosed in Applicant's co-pending application does not benefit from the advantages inherent in the prior art solid single board plank and laminated plank.
It would be beneficial to the prior art to construct a scaffolding plank that optimizes and combines the advantages of both the single solid board plank and the laminated plank while greatly reducing, if not eliminating, their respective disadvantages.
Scaffolding planks are however strictly regulated. The Occupational Safety and Health Administration, OSHA, as well as the Southern Pine Inspection Bureau, SPIB, outline strict standards for scaffolding planks. Pursuant to such regulations, scaffolding boards must comply with certain width, breakage, and quality standards. The OSHA and SPIB standards are strict because workers entrust their lives to the scaffolding. The prior art would thus benefit from a scaffolding plank, as described above, that meets and preferably exceeds the OSHA and SPIB standards. The OSHA standards found at 19 C.F.R. .sctn. 1926, Subpart L, including Appendix A, recommends scaffolding for typical medium loads to be 2".times.10" (nominal). (Dimensions described in this specification are nominal dimensions, unless otherwise noted. Nominal dimension units are typically 1/2" greater than actual size dimensions.)
Because the lives of workers hinge on the integrity of scaffolding planks, any safety factors that can be added to a scaffolding plank greatly enhance the value of the scaffolding plank. It would be beneficial to the prior art to provide a scaffolding plank, as described above, which also includes an additional worker safety factor.
Moreover, so workers do not slip while stepping on the scaffolding planks, it is important for the scaffolding planks to have a non-slippery top surface. Natural wooden boards are typically smooth, and must be manipulated to be provided with an artificial non-slippery top surface. However, such manipulation normally also weakens the board. It would thus be beneficial to the prior art to provide a scaffolding plank that includes a non-slippery top surface. It would also be beneficial to the prior art to provide such a non-slippery scaffolding plank that includes natural wooden boards that have not been weakened during any artificial surface texturing.
Manufactured wide boards for scaffolding are unknown to the prior art. Prior references, however, disclose structural wood assemblies formed from a plurality of smaller wood boards. Illustrative of such wood assemblies are U.S. Pat. No. 2,650,395 that issued to de Anguera on Sep. 1, 1953, U.S. Pat. No. 5,120,378 that issued to Porter et al. on Jun. 9, 1992, U.S. Pat. No. 4,534,448 that issued to Trainer on Aug. 13, 1985, U.S. Pat. No. 1,167,988 that issued to Faulkner on Jan. 11, 1916, U.S. Pat. No. 2,569,450 that issued to Bouton on Oct. 2, 1951.
The assembly shown in U.S. Pat. No. 2,650,395 discloses a method of forming wood flooring from relatively narrow pieces of wood having varying lengths. The pieces of wood are placed in a number of parallel rows wherein the pieces are placed end to end. A plurality of spaced thin connector keys are driven into lateral bores in the aligned pieces and hold the pieces together.
U.S. Pat. No. 5,120,378 discloses an apparatus and method for producing a prestressed wood material beam. The wood beams are held together using adhesives or mechanical fasteners such as nails or staples.
U.S. Pat. No. 3,144,892, issued Aug. 18, 1964 to Webster, discloses and claims a method of fabricating panels that are formed by attaching a plurality of boards with relatively soft metal dowels. The dowels are driven into aligning bores that have been drilled through the narrow boards. Webster differs or teaches away from the present invention by having at least three significant limitations. First, Webster orients the plurality of boards such that their wider sides are contiguous. The present invention orients the boards so that their narrower sides are contiguous. This orientation is difficult to achieve without splitting the boards, but is achieved by the disclosed method. Second, Webster uses boards that have a tongue-and-groove channeling between boards to align them. The present method uses flat boards that are aligned with flat sides adjacent and tightly positioned together by the disclosed board pinning machine. Webster further requires tongue-and-groove channeling for releasing cuttings from bores during the drilling operation. Third, Webster uses the groove channels in the boards to "function as lead holes for starting the drill tips into each succeeding panel component" when drilling bores for the securing metal dowels. The present invention, due in part to its board pinning machine securely holding the boards, bores holes directly through the smaller boards without the need for pilot or lead holes.
U.S. Pat. No. 2,118,048, issued to Landsem, discloses a combined use of natural and laminated boards for fabricating structural beams, joists, girders, airfoils and other support components. U.S. Pat. No. 2,230,628 issued to Sahlberg likewise teaches the use of natural wood and laminate boards to fabricate box beams and I-beams girders. However, such mixing of natural and laminate boards is novel in the area of scaffolding boards. Landsem and Sahlberg teach structures having relatively large height versus width ratios. Adapting such structures to a scaffolding plank would result in a heavy, thick plank that would not be useful or commercially viable.
British Patent No. 720,603, issued to Elvins discloses a plank that comprises a metal frame formed by a pair of side members having stepped ends and end members shaped to overlap the said ends, one or more longitudinal metal partition strips, and wood pieces situated in the spaces between the said strips and frame. The strength in the design disclosed by Elvins is in the metal frame and metal partition strips, making the wooden slats inserts for the walking surface. The Elvins invention does not utilize the strength is characteristic of the wood used, and requires the use of metal frames that are heavier than wood, and are more difficult to maintain and use. The planks taught by Elvins have indented ends that may not be useful in standard scaffolding frames, especially those used in the U.S.
Though the above mentioned devices and assemblies may be helpful for their intended purposes, none disclose a manufactured scaffolding plank that meets OSHA and SPIB requirements and that optimizes and combines the advantages of both the single solid board plank and the laminated plank while greatly reducing, if not eliminating, their respective disadvantages.